As disclosed in Canadian Patent Application 2,514,916 and corresponding issued U.S. Pat. No. 8,082,734 by St. Denis reciprocating pumps are extensively used on oil wells and they generally consist of a polish rod with cooperating valves that serve to pump liquids to surface as the polish rod is reciprocated in the well. According to St. Denis a drive assembly is provided for a reciprocating pump which includes a support structure and a linear actuator mounted on the support structure. The linear actuator has a stationary portion and a movable ram portion. At least one direction altering cable guide is mounted to the movable ram portion of the linear actuator. At least one cable is provided having a first end and a second end. The first end is anchored to one of the support structure or the stationary portion of the linear actuator. The second end is adapted for attachment to a polish rod of a reciprocating pump. As the movable ram portion moves, the cable and cable guide configuration provide a mechanical advantage which results in the polish rod reciprocally moving a multiple of the distance traveled by the movable ram portion of the linear actuator. The movable ram portion is driven by a rotating screw with a travelling nut; however, the mechanism requires use of additional shock absorbers to slow the movement of the travelling nut in the event of a power loss such that the resulting mechanism is complex and may require considerable maintenance to operate.